1. Field of the Invention
The present invention relates to a light emitting device for lighting a light emitting diode (LED) by means of a lighting circuit.
2. Description of the Invention
Up to now, as a device of this kind, there has been disclosed a light emitting device for simultaneously lighting light emitting diodes of a light emitting unit by making a lighting circuit receive a DC power from a DC power source, said light emitting unit being formed by arranging a plurality of light emitting diodes and connecting these light emitting diodes with each other (see Patent Document 1 for example). This light emitting device is configured so that a DC power is inputted into a switching regulator of the lighting circuit from a DC power source and this switching regulator performs a switching operation according to the magnitude of electric current flowing through the light emitting unit. And it is configured so that a pulse current obtained by the switching operation of the switching regulator is smoothed into a direct current by a smoothing circuit and supplied to the light emitting unit.
In a light emitting device configured in such a way, since a constant-current circuit is formed out of a switching regulator and a smoothing circuit, a current limiting resistor does not need to be provided and no efficiency degradation is caused by some voltage drop and a high efficiency can be maintained. And even when fluctuation in voltage drop of light emitting diodes is caused by a voltage fluctuation of a DC power source or a temperature change, since an electric current flowing through light emitting diodes is kept at a constant value and a proper loaded state is maintained, sufficient luminance brightness and high reliability can be obtained.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 1999-68161 (claim 1, Paragraph [0006], Paragraph [0017])